Class insects (Insecta). Insect movement Insect movement
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The subtype Tracheal (Tracheobreathing) includes terrestrial and secondary aquatic arthropods in which gas exchange is carried out using tracheas. The subphylum is divided into 2 classes: Centipedes and Insects. The class of insects unites the most highly organized representatives of this subtype and is the most numerous not only among arthropods, but also among all other animals. Over 1 million species of insects are known, and many entomologists believe that this number is greatly underestimated and that in reality there are more than 2 million species of insects living on our planet.
Numerous adaptations have allowed insects to occupy all ecological niches. No other group of invertebrates can compete with them in the diversity of adaptations to different living conditions. In addition, insects are the only group of invertebrates capable of active flight, which allowed them to also conquer airspace. Currently, insects are the most prosperous group of animals on our planet, both in terms of the total number of individuals and the number of species, and in terms of the breadth of distribution and differentiation.
Characteristic signs distinguishing insects from other arthropods are the following: respiratory organs - trachea; the body is divided into a head, thorax and a segmented abdomen, with the thorax consisting of three segments; three pairs of walking legs; on the head there is one pair of antennae.
Along with morphological features, insects have a whole complex adaptations to life on land: impenetrable cuticle; excretory organs - Malpighian vessels, which allow saving water in the body; the presence of a fat body - a source of metabolic water; internal fertilization.
General characteristics of the class Insects. Let us consider the main characteristic morphophysiological features of this class.
External building. The head of insects consists of an acron (head lobe) and four segments fused together. The head is surrounded on top and sides by a durable chitinous capsule. On its sides there are two compound eyes, between which there may be simple ocelli.
On the head lobe there is a pair of segmented antennae, which are homologous to the first pair of antennae of crustaceans. The antennae of insects are organs of touch and smell; in different species they vary in length and shape; they can be feathery, comb-like, bristle-shaped, etc. The first segment of the head of insects is reduced, so the second pair of antennae (as in crustaceans) is not formed. The remaining three segments of the head contain modified limbs. Located around the mouth opening, they collectively form the oral apparatus. The structure of the oral apparatus of insects depends on the nature of the food and the method of feeding. Mosquitoes have a piercing-sucking type of mouthparts, bees have a lapping type, butterflies have a sucking type, and flies have a licking type (Fig. 52). The general structural plan underlying the organization of all types of mouthparts can be considered using the example of a gnawing mouthpart (see Fig. 52). It is considered the primary one, from which all other types of oral apparatus originated, which was associated with the transition to feeding on liquid food.
The gnawing oral apparatus includes appendages of the second segment of the head - upper jaws, or mandibles. They are powerful jagged chitinous plates used for biting and crushing solid food. Appendages of the third segment - lower jaws, splitting food ( first maxillae). Fused appendages of the fourth segment - second pair of mandibles (second maxillae), which form an unpaired lower lip. The oral apparatus also includes the upper lip, which is an outgrowth of the cuticle, and language- chitinous protrusion of the floor of the oral cavity. Beetles, cockroaches, grasshoppers, butterfly caterpillars and many others have gnawing mouthparts.
With the help of a thin constriction (neck), the head is movably connected to the chest. The thoracic region consists of three segments, which are called prothorax, mesothorax and metathorax (Fig. On the ventral side, a pair is attached to each segment of the chest walking legs. Depending on the method of movement and the function performed, the legs of insects can be running, digging, jumping, swimming, etc.
Most insects have paired pairs on the dorsal side of the second and third thorax segments. wings. The wings are two-layer outgrowths of the body wall. In the thickness of the wing there are channels with tracheas and nerves. They form so-called veins that perform a supporting function. The structure of the wings and venation are an important systematic feature. In different groups of insects, the fore and hind wings are developed to varying degrees. Primitive insects (dragonflies) have identical pairs of wings. In some orders, the first pair of wings turns into hard elytra. Such insects (for example, beetles) fly on a second pair of wings. In dipterans (flies, mosquitoes) only the first pair of wings is developed, and the second is reduced and turned into halteres. Among insects there are also wingless species. Some of them are primarily wingless (springtails, doubletails). This is an ancient primitive group. The other part consists of secondary wingless insects that have lost their wings due to the peculiarities of their lifestyle (fleas, lice, etc.).
Based on the method of attaching the wings to the body and the type of movement, insects are divided into ancient and new-winged insects. In ancient winged birds (dragonflies and mayflies), the wings move in the same plane (up and down). In other insects, the wings rotate around an axis in flight, making a figure eight with their apex. The abdomen of insects can consist of a different number of segments. In primitive forms, the abdomen includes up to eleven segments and an anal lobe. In other groups, the number of segments is reduced to four or five. The limbs on the abdomen are usually absent, but in some species their rudiments may remain.
Integument and muscular system. The body of insects is covered with a three-layer cuticle, which is secreted by the surface epithelium - the hypodermis. The outside of the cuticle is covered with a lipoprotein layer, which reduces water evaporation. Therefore, in addition to its supporting and protective functions, the cuticle also protects the insect’s body from water loss. On the surface of the cuticle there are movable hairs, scales, and bristles. Various glands are formed in the hypodermis: poisonous, odorous, molting, waxy.
Pigments contained in the cuticle or hypodermis determine the color of insects. The main pigments are melanins, whose color varies from yellow and brown to black. In addition to them, there are pigments of yellow and red tones. Many insects have a protective coloration. This allows them to hide from enemies and sneak up on prey.
The chitinous cuticle forms internal projections to which muscles and internal organs are attached. The skeletal muscles of insects are formed striated muscle tissue and consist of individual muscle bundles, the number of which can reach 1.5-2 thousand. Individual insect muscles are capable of an extraordinary frequency of contractions. Thus, the muscles that control the movement of the wings are capable of contracting at a frequency of up to 1 thousand times per second. This is due to the fact that the muscle responds to one nerve impulse with a series of contractions. A differentiated muscular system allows insects to perform very complex movements.
Digestive system. The digestive system begins with the oral opening leading into the oral cavity, into which the ducts of several pairs of salivary glands flow (Fig. 54). In butterfly caterpillars, the second pair of salivary glands is modified into arachnoid or silk-secreting glands.
The foregut is ectodermal in origin and is lined with cuticle. In most species, this section of the digestive system is divided into the pharynx, esophagus (often expanding into a crop) and stomach. The pharynx and esophagus serve to carry food, and it accumulates in the goiter. In insects that feed on solid food, the stomach has muscular walls with thick chitinous teeth. Food is crushed in it. In the short endodermal midgut, final digestion and absorption of food occurs. The posterior ectodermal gut is long. Its main functions are the formation of feces, the reabsorption of water and the removal of excrement through the anus at the end of the abdomen.
In herbivorous species, cellulose digestion is ensured by intestinal symbionts (protozoa and bacteria) capable of secreting the enzyme cellulose.
Excretory system. The main excretory organs in insects are malpighian vessels- long thin tubes, the number of which varies from 2 to 200 pieces (see Fig. 54). They are located at the border of the midgut and hindgut, but are of ectodermal origin and develop from the hindgut. One of the ends of the tubes is blindly closed, and the other opens into the intestinal cavity. Metabolic products dissolved in the hemolymph enter the Malpighian vessels. There they turn into an insoluble form - crystals uric acid and are excreted together with excrement. The released water returns to the hemolymph. This organization of the excretory system significantly reduces water loss, which allows insects to live in hot and dry climates.
8.Additionally, the excretory function is performed accumulation buds: fat body and pericardial cells. Pericardial cells are located near the heart. Their main function is the absorption of toxic substances from the hemolymph. The fat body of insects is very well developed and plays an important role in life processes. Firstly, it stores nutrients, which allows the animal to go without food and water for a long time. Secondly, metabolic products (uric acid salts and other excrements) accumulate in the cells of the fat body. In the form of crystals, they remain in it until the end of life. In some insects (fireflies), modified areas of the fat body form luminescent organs. Partial metabolic products are deposited in the cuticle and removed during molting.
Respiratory system. The respiratory organs of insects are represented only by trachea- branching tubes of ectodermal origin. The trachea is lined with a cuticle, which forms spiral thickenings. This prevents the trachea from flattening during movement and bending. The tracheas begin with paired respiratory openings located on the sides of the mesothorax, metathorax and abdominal segments. The largest tracheas are united into rows of longitudinal trunks connected by bridges. The thinnest terminal branches of the trachea entwine all the internal organs, the fatty body, and can even penetrate into individual cells. This significantly increases the efficiency of gas exchange, which is especially important during intense muscle work.
Circulatory system. Circulatory system open The heart is located on the dorsal side in the abdomen. The cavity of the heart is divided into chambers, the aorta extends forward from it, the posterior end of the heart is blindly closed. When the chambers contract, hemolymph is released through the aorta into the body cavity, washes the internal organs and returns back to the heart through holes in its side walls. Due to the presence of tracheal breathing, the main functions of the circulatory system are the delivery of nutrients from the digestive system to the internal organs and parts of the body and the transport of metabolic products to the excretory organs. Hemolymph also transports hormones secreted by the endocrine glands.
Nervous system and sensory organs. The nervous system of insects, like other arthropods, is represented by ventral nerve cord. Brain ( paired suprapharyngeal node) is well developed and has a complex structure. Its upper section innervates the head lobe and eyes, the middle section innervates the antennae, and the posterior section innervates the upper lip.
The upper part of the brain also includes the so-called mushroom bodies, which control complex movements and reflex activities. Therefore, they are most well developed in social insects with complex behavior.
In the abdominal nerve chain, the nerve ganglia of the thoracic segments reach their maximum development, as they innervate the legs and wings. Except somatic nervous system, insects have a well-developed vegetative ( sympathetic) nervous system, which controls the activity of internal organs.
Along with ordinary nerve cells, there are neurosecretory cells in all parts of the nervous system of insects. Together with the endocrine glands, they participate in the humoral regulation of the body.
Sense organs insects are complex and diverse, which is associated with a high level of organization and complex behavior of these animals. Insects are able to perceive all main types of irritations. Moreover, their sensory abilities, as a rule, exceed those of higher vertebrates. For example, many insects see in the ultraviolet spectrum, the hearing organs of many moths perceive ultrasound, and a male silkworm is able to detect a female by smell at a distance of several kilometers. The visual organs of insects are represented by simple and complex - faceted - eyes. Many insects (butterflies, bees, ants) have color vision.
Reproduction and development. Insects dioecious. In many species it is expressed sexual dimorphism, which manifests itself in unequal body size, coloring, the presence of wings, the development of various body appendages and the structure of the genital organs. For example, in many butterflies, males and females differ in color, and in fireflies, females, unlike males, do not have wings.
The gonads are located in the abdomen. Female reproductive system consists of paired ovaries and oviducts, which, merging, form an unpaired tube that continues into the vagina. The vagina also opens into a sac-like spermatic receptacle, which serves to store sperm after mating. In a number of species (bees, ants, etc.), sperm remains viable for a long time. For example, a queen bee mates once in her life and lays fertilized eggs for five years. Often, females develop egg-laying organs - ovipositors (for example, the saber-shaped ovipositor in grasshoppers).
Male reproductive system formed by paired testes and long vas deferens, which merge into the unpaired ejaculatory duct. Fertilization is internal; males may have a developed copulatory organ.
According to the type of development, insects are divided into two groups - with incomplete and complete transformation (metamorphosis). When developing with incomplete transformation In the life cycle of an insect, the following stages alternate: egg - larva - adult insect (imago) (Fig. 55). The larva, hatched from the egg, looks like an adult insect. They have a common body plan, the same type of oral apparatus, and therefore a similar type of nutrition, and they usually live in the same environmental conditions. Larvae differ from adults in the underdevelopment of their wings, the absence of secondary sexual characteristics, and sometimes the presence of special larval organs. With each molt, the resemblance to an adult insect increases more and more. Incomplete transformation is typical for grasshoppers, cockroaches, and bedbugs.
In insects with complete transformation the number of stages increases: egg - larva - pupa - adult insect (imago) (Fig. 56). The larvae of such insects are fundamentally different from adult insects in their general body plan; as a rule, they have a different type of mouthparts and a different type of nutrition (for example, caterpillars have a gnawing mouthpart, and butterflies have a sucking mouthpart with a proboscis). They often live in different environments (for example, a mosquito lives on land, while its larva lives in water). This allows adults and larvae not to compete for food. After the last molt, the larva goes into a dormant state - pupates. Under the shell of the pupa, the larval tissues are first destroyed, and then the tissues and organs of the adult insect are formed. Development with complete metamorphosis is characteristic of the most highly organized insects (beetles, butterflies, hymenoptera, diptera).
9.
§ 20. The diversity and importance of insects
The class of insects is divided into large systematic groups: subclasses, infraclasses, orders. This classification is based on such important features as the structure of the wings, the type of oral apparatus, and features of postembryonic development. According to modern concepts, the class of insects is divided into 2 subclasses: Primary wingless and winged.
Primary wingless insects are ancient, most simply organized insects without wings. They have a chewing mouthpart and three long, segmented appendages at the posterior end of the body. The primary wingless species include the order Bristletail, or Silverfish. They received their second name for the shiny scales covering their body. Unlike other insects, the development of silverfish occurs without transformations; their small larvae are similar to adults. Primary wingless insects usually live in human dwellings or in the soil, participating in soil-forming processes.
Winged animals are more highly organized animals. They are divided into two groups: with incomplete and complete transformation. Let's look at the characteristic features of some of the most common orders of insects.
Orders of insects with incomplete metamorphosis. Characteristic stages of development of insects from this group: egg - larva - imago.
Order of Dragonflies (about 4.5 thousand species). Dragonflies are one of the most ancient groups of insects known from fossil remains from the Carboniferous. Adult dragonflies are large predatory insects that hunt in flight. They have long transparent wings with a dense network of veins, a mobile head with large faceted eyes, a gnawing mouthparts and short antennae (Fig. 57). Dragonflies develop in water. The eggs hatch into predatory larvae (naiads) that do not resemble adults. They feed on the larvae of insects and other aquatic invertebrates, capturing them with a modified lower lip (mask). Naiads breathe oxygen dissolved in water using special organs - tracheal gills. Naiads move along the bottom using their legs, and swim by pushing a stream of water from their hindgut. The last instar larvae emerge from the water and molt, forming an adult insect (imago).
Order Cockroaches (about 2.5 thousand species). Most cockroaches are inhabitants of the tropics, but there are species that are found everywhere in human dwellings (black cockroach and red cockroach, or Prusak) (Fig. 58). Cockroaches are omnivorous; in natural conditions they feed as saprophages.
They have a flattened body, long thin antennae, and a gnawing mouthpart. The front wings are leathery, the hind wings are membranous, folding like a fan. Cockroaches lay their eggs in a special cocoon (ootheca), from which small larvae emerge, similar to adult insects.
Order Orthoptera (more than 20 thousand species). Insects of medium and large sizes. The first pair of wings forms leathery narrow elytra, the second pair is wide, thin, membranous, fan-shaped, sometimes underdeveloped. The mouthparts are gnawing. The third pair of walking legs is elongated, jumping type.
Most orthoptera (grasshoppers, locusts) live in open spaces: fields, meadows, and steppes. They are distinguished by the ability to jump, often turning into flight. Crickets live on the soil surface and in human dwellings (Fig. 59). Mole crickets make tunnels in the soil, damaging plant roots. Many Orthoptera have organs of sound and hearing. The chirping is specific to each species and serves to attract females to the male. Male grasshoppers and crickets chirp using their wings, and male locusts make sounds by rubbing their hind legs against their wings.
Locusts and mole crickets cause enormous damage to agriculture.
At the end of summer, female locusts use an ovipositor to lay a packet of eggs - an egg capsule - into the soil. In spring, wingless larvae emerge from the eggs. They gather in dense flocks and migrate in search of food. Locusts feed on different types of plants, completely destroying both natural biocenoses and agricultural crops. After several molts, the larvae turn into adult winged insects capable of long-distance flights. A swarm of adult locusts can fly at a speed of 10-15 km per hour and fly 80-120 km in a day. Along the path of their movement, the locust completely destroys vegetation. A swarm of locusts can turn thousands of hectares of crops into desert in 1-2 hours. Locust control is carried out using chemical methods of protection.
Order Hemiptera, or Klupi (more than 30 thousand species). Externally, they are very diverse terrestrial and aquatic insects with piercing-sucking mouthparts. The first pair of wings is usually heterogeneous: the apical part is thin, and at the base it is more dense, leathery; the second pair is membranous. Sometimes the wings are missing. Adult bedbugs have scent glands. Among them there are both herbivorous and predatory species, some are bloodsuckers.
Many predatory bugs live in water: smoothies, water striders, water scorpions. Some of them are capable of attacking large prey (other insects, tadpoles and fish fry).
Water striders live on the surface of the water - bugs with a thin, rod-shaped body and long thin legs. They run quickly on the surface film of water. Among water striders there is, perhaps, the only species of true oceanic insects - the sea water strider halobates. It is found at a distance of several thousand kilometers from the coast.
Among the ground bugs, the blood-sucking bed bug bothers humans the most. In nature, its closest relatives live in caves and nests, feeding on the blood of birds and bats. Among herbivorous bugs there are many pests of agricultural crops. The greatest damage to the wheat crop is caused by the turtle bug. Recently, great interest has been shown in terrestrial predatory bugs that feed on insects and ticks. They can be used to control agricultural pests.
Orders of insects with complete transformation. Characteristic stages of development of insects from this group: egg - larva - pupa - imago.
Order Coleoptera, or Beetles (more than 250 thousand species). A distinctive feature of the representatives of the order is the transformation of the front pair of wings into hard elytra. Beetles fly only with the help of a rear pair of membranous wings. The elytra protect the wings and the soft dorsal side of the abdomen. During flight, the elytra are raised, moved to the side and resemble the bearing planes of an airplane, and the rear wings act as propellers. The mouthparts are of a gnawing type with powerfully developed upper jaws; beetles feed on solid food. The size of the beetles varies from 0.3 to 150 mm.
Most beetle larvae have a large head with gnawing jaws and three pairs of legs. Some larvae may have reduced legs (bark beetles, longhorn beetles). The respiratory organs of larvae are more diverse than those of adult beetles. Some aquatic inhabitants, for example, breathe using tracheal gills. During the development period, the larvae molt several times.
The female cockchafer lays eggs in the soil and then dies. The larvae that emerge from the eggs live in the soil litter and feed on humus. In winter, the larvae go deep into the ground to escape freezing, and next spring they rise to the surface and begin to feed on the roots of herbaceous plants. After the second winter in the soil, the larvae begin to eat the roots of shrubs and trees, causing the death of young plants. The larvae have a thick, whitish, slightly curved body (Fig. 60). There are three pairs of jointed limbs on the thoracic segments. The body is covered with a soft chitinous covering, only on the head and limbs the chitinous covering is darker and denser. Through the thin covers of the larvae, the trachea and intestines filled with food are visible. After the third winter in the country, the larva pupates. The pupa already bears some resemblance to the adult beetle. Through the dense chitinous covers, you can see the head with oral limbs, eyes and antennae, as well as folded limbs and the rudiments of wings on the chest. The pupa is motionless and does not feed. In the fall, an adult beetle emerges from the pupa, overwinters in the ground and rises to the surface only in the spring of the following year.
Order Lepidoptera, or Butterflies (about 140 thousand species). Butterflies have two pairs of wings, densely covered with microscopic scales. The color, structure and placement of scales determine the variety of colors and patterns of wings. The sucking type mouthparts look like a coiled proboscis, with the help of which butterflies drink nectar or sweet plant juice.
Butterfly larvae are caterpillars with gnawing type mouthparts. The chest segments bear a pair of jointed limbs with claws; the abdomen usually has 5 pairs of false legs. Caterpillars feed on plant leaves.
Many butterflies are pollinators of angiosperms, and their caterpillars cause serious damage to plants.
Cabbage white butterflies (cabbage butterflies) lay eggs on the underside of leaves of cabbage and other cruciferous plants. Small yellow caterpillars emerge from the eggs. They feed actively, grow quickly and molt several times. The body of the caterpillars becomes bluish-green with three yellow longitudinal stripes and black dots and is densely covered with hairs. From the cabbage leaf on which the caterpillars fed, only large veins remain. The caterpillars crawl into secluded places and pupate. After a certain time, butterflies emerge from them. Over the summer, two generations of cabbage whites usually develop.
The silkworm butterfly can rightfully be considered a domestic insect, because this species does not occur under natural conditions. The homeland of the silkworm was the Himalayas, from where it was brought to China, where 2.5 thousand years BC. e. Sericulture began to develop. The silkworm came to Russia more than 300 years ago. Over thousands of years in captivity, butterflies have lost the ability to fly. The salivary glands of silkworm caterpillars are transformed into spinning or silk-secreting glands. They form a secretion that hardens in the air, turning into a silk thread. When building a cocoon, the caterpillar wraps itself in a silk thread, which can reach a length of a thousand meters. Despite the development of the chemical industry and the production of artificial silk, sericulture is a profitable branch of agriculture.
Order Diptera (about 150 thousand species). The main feature of the representatives of the order is the presence of one first pair of membranous wings. The second pair is reduced and represents short club-shaped appendages - halteres (organs of balance and stabilization during flight). Another characteristic feature is the absence of legs in the larvae. The chest segments of Diptera are fused with each other.
Diptera are divided into 2 suborders: Long-whiskered, or Mosquitoes, and Short-whiskered, or Flies (Fig. 62).
The rate of reproduction of the housefly is amazing (see Fig. 62). At one time, the female lays 100-150 eggs, and if there is a sufficient amount of food, the fly lays eggs several times in a row with an interval of 2-4 days. It is estimated that if all the larvae, pupae and flies themselves survived, then during the summer season the offspring of one fly could exceed 5 trillion copies.
Fly larvae (maggots) live in cesspools, latrines, garbage dumps - where rotting organic debris accumulates. They are deprived not only of limbs, but also of the head capsule. The larvae secrete digestive enzymes that promote rapid decomposition and liquefaction of organic residues. As a result, the larvae swim in liquid, semi-digested food, which they constantly swallow. This method of nutrition is called extraintestinal. The larvae grow quickly and soon pupate. The barrel-shaped pupa of flies has a dense brown shell and is called a puparium.
In appearance, gadflies resemble a large black fly. Their main feature is the underdevelopment of the oral organs and digestive system. Adult gadflies do not feed; they live off the nutrients accumulated by the larva. Females lay eggs on the fur of animals (dermal gadflies) or in the nostrils, mouth, eyes of animals and humans (cavitary gadflies). Botfly larvae emerge from the eggs and burrow under the skin, where they actively feed and grow. In spring, the larvae leave their host and pupate in the ground. An adult insect emerges from the pupa.
Many social species of Hymenoptera exhibit polymorphism. It is especially clearly expressed in ants, where various forms of worker ants and soldiers are found in the same family. This is due to the variety of actions they perform.
Ants are a large group of social insects with complex behavior. Forest red ants build high cone-shaped nests - anthills. The family consists of several thousand individuals with clearly defined polymorphism. It consists of wingless workers (underdeveloped females), winged males (who die after mating) and winged founder females. Many ant species have a division of labor between workers. There are soldier ants, forager ants, and ants that care for the larvae. Ants overwinter in the underground part of the anthill, where a constant temperature is maintained.
Ants reproduce and disperse once or twice a year. This is preceded by the appearance of many winged ants in the anthill. These are young males and females who at a certain moment leave the anthill and rush into flight. Mating occurs in the air or on the ground, shortly after which the males die. The females lose their wings and begin to look for a place suitable for establishing a new anthill. They dig a small hole and lay their first small batch of eggs. White worm-like larvae emerge from the eggs, which the female begins to feed. The larvae pupate and worker ants emerge from the pupae. After this, the female's only concern is laying eggs, and all other functions are performed by the worker ants.
Forest ants feed mainly on insects and their larvae, destroying a huge number of pests. They also play an important role in soil formation processes: they loosen the soil and enrich it with organic matter. Bees are social insects with complex behavior. Bees live in families (40-70 thousand individuals each) in hives or tree hollows. In a family there is one large female (queen), several hundred males (drones), and all the rest are worker bees (Fig. 63). The queen lays up to 1 thousand eggs daily. Worker bees are females that are unable to reproduce. Their ovipositor is turned into a sting connected to a pair of poisonous glands located in the abdomen. The structure of the sting is such that when it bites, it gets stuck in the victim and breaks out of the bee’s abdomen with part of the internal organs. Therefore, after being stung, the bee dies.
The nectar that bees collect turns into honey in their crops. The bees themselves feed on honey and feed the larvae. Bees use wax to raise larvae and store honey.
honeycombs are vertical rows of hexagonal-shaped cells. The wax is secreted by special glands on the bee's abdomen and hardens in the form of thin plates. The bee removes these plates with its paws, then softens the wax with its jaws and fashions a honeycomb from it.
The bee's body is densely covered with numerous hairs, to which pollen easily sticks. Using special combs located on the legs, the bee cleans pollen from the hairs and transfers it to the recesses covered with bristles on the legs of the third pair of legs - the baskets. Having filled the crop with nectar and the baskets with pollen, the bee returns to the hive. There, the bees shake pollen into the honeycombs and fill them with honey - beebread is formed (food for the larvae).
Beginning in spring, the queen lays one fertilized egg in each cell of the comb. The eggs hatch into worm-like larvae, which the worker bees feed with royal jelly for the first 5 days and then with beebread. Royal jelly is secreted by special glands located on the bee's upper jaw. The larvae then pupate, and after 2 weeks a young worker bee emerges from the pupa. As the bee colony grows, worker bees begin to build large cells for the development of new queens. In order for the larva to develop into a queen, it is fed only royal jelly throughout its development. From unfertilized eggs in cells, drones develop - haploid males.
Before the young queen leaves the cell of the honeycomb, the old queen leaves the hive with part of the worker bees, swarming, or division of the family, occurs. The young queen flies out of the hive along with the male drones to mate. After the mating flight, she returns to the hive and begins laying eggs. In the female's spermatozoa, sperm remain alive for several months. Drones that have fertilized a young female are killed by worker bees and thrown out of the hive.
Bees have very complex and varied behavior. During its life, the same bee changes its professions in the hive. First, immediately after leaving the honeycomb, young bees clean the old cells and feed the larvae with beebread. As the glands that produce milk develop, they feed the larvae and queens. After this, the bee becomes the recipient of food from the arriving bees and distributes it throughout the hive. As soon as the wax glands begin to produce wax, the bees begin construction work. Later, the poison glands begin to function, and the bee becomes a guard at the entrance to the hive. And only at the end of their lives do bees begin to collect nectar and pollen.
Forager bees, having discovered rich food areas, communicate them to all other bees in the language of dance. By wagging its belly and writing figure eights, the bee conveys information about the amount of food, the direction and distance to it. The information obtained allows the bees to accurately find the indicated places. The social life of bees and ants gives them many advantages over solitary species. Social insects are better protected from enemies, successfully collect food together and endure frosty winters. By caring for the offspring, they ensure the almost complete survival of individuals at the larval stage. All this allowed social insects to become the most prosperous group of animals.
General characteristics. The class of insects includes tracheal-breathing arthropods with a characteristic division of the body into the head, chest and abdomen (Fig. 146). The head contains one pair of antennae, eyes and a mouth with three pairs of jaw appendages. The chest, as a rule, consists of three segments, each of which has a pair of limbs (hence another name for insects - hexapods). Most insects have a pair of wings on the second and third thoracic segments. The abdomen, consisting of 6-12 segments, is devoid of limbs, and only in some of them are they preserved in a modified form and perform special functions (ovipositor, etc.).
Rice. 146. Dismembered insect (stag beetle Lticanusservtis):
1 - underlip; 2 ~-lower jaw; 3 ......-mandible; 4 - upper lip; 5 - head;
V- antennas; 7
- middle chest; I, 11, 14-- thoracic limbs; U- front pair of wings (elytra); 10-
mesothorax; 12
back chest; 13
-- .chadpne wings;
15
abdomen
More than half of all animal species living on Earth belong to the class Insects. There is no corner of the earth where they do not meet. The role of insects in nature and human economy is enormous.
The class Insects includes subclasses: Primary wingless (Apterygota)
and Winged
(Pterygoid).
Structure and vital functions. The appearance of insects is very diverse. This applies to both body size, coloring, and the structure of the articulated appendages of the head, chest and abdomen. Thus, the antennae on the head are short and long, in the form of setae and pinnately branched, thin and lamellar, etc. The oral organs in the number of three pairs are represented by the upper jaws (mandibles), lower jaws (maxillae) and the lower lip formed by the fusion of the second pair lower jaws. All of them developed in the process of evolution from articulated appendages of the head segments.
The structure of the oral organs of insects of different systematic groups varies widely, reflecting the diversity in feeding methods. There are four main types of mouthparts: gnawing, gnawing-sucking, piercing-sucking and sucking (Fig. 147).
Gnawing mouthparts are characteristic of insects that feed mainly on solid food - beetles, cockroaches, orthoptera, etc. Their upper jaws - mandibles - have the appearance of massive chitinous plates with jagged sharp inner edges. The first pair of mandibles (maxillae) consists of several segments and bears mandibular palps, and at the ends - paired lobes, the inner of which is lined with chitinous setae. Both the mandibles and the lower jaws serve the insect for separating and crushing food. The second pair of mandibles fuses in its main parts into a single dissected plate, forming the lower lip, on the side of which the lower labial palps are located. The oral palps have tactile hairs and pits for the organs of touch and taste. The lower lip covers the mouth and its organs from below; from above it is limited by a chitinous plate (fold) - the upper lip.
Gnawing-sucking mouthparts are present in insects that feed on both liquid (nectar of flowers) and solid food. These are, for example, the mouthparts of bees and bumblebees. Their upper jaws look like a pair of blades serrated along the inner edge. The lower jaws are elongated into lanceolate plates with rudimentary palps. The lower lip continues forward with a thin tongue formed by folded internal lobes. When the lower jaws are applied to the tongue, a tube is formed - a proboscis, with the help of which the insect sucks nectar.
Rice. 147. Mouthparts of insects:
/ - gnawing (cockroach); // - gnawing-sucking (bees); /// - sucking (butterflies); IV- piercing-sucking (female mosquitoes);
/ - upper lip; 2-
upper jaws;
3
- lower jaws; 4
- underlip; 5 -
subpharyngeal; 6
- mandibular palps; 7 - lower labial palps
Piercing-sucking mouthparts characteristic of mosquitoes, bedbugs, aphids and some other insects. Their mouthparts are greatly elongated and, folding, form a proboscis, which serves to suck blood or plant juice. For example, in female mosquitoes, the lower lip has the form of a groove, open at the top, ending in two petals. The remaining mouth parts lie in the recess of the gutter.
The upper lip, with edges curved downwards, almost closing, forms a channel through which food is absorbed. The gap on its lower side is closed by a long, pointed subpharyngeal end. It has a salivary duct inside. The mandibles and maxillae lie nearby. They are in the form of elastic, prickly bristles. The upper lip, subpharynx and jaws are involved in applying the injection, and the lower lip bends as the piercing apparatus is immersed in the wound.
sucking horny organs characteristic of butterflies (Lepidoptera) and are arranged in the form of a sucking proboscis. The upper and lower lips, the upper jaws are greatly reduced. The lower jaws are large and have the appearance of flexible long grooves. When folded, the grooves form a long, hollow inside proboscis. In the resting state, it is curled In a molten form, the proboscis is immersed like a butterfly into the corolla of the flower.
The structure of the legs of insects is very different depending on the lifestyle and method of movement (Fig. 148). They consist of the following segments: the main one is the coxa, behind it there is a small segment - the trochanter, which facilitates the movement of the limb. Then there are two long segments - the thigh and the lower leg, which contain strong muscles. The leg ends in a tarsus of several small segments, the last of which usually has 1-2 claws.
The wings are formed as thin and flat folds of the integument of the second and third segments of the chest (Fig. 149). They are plates of various shapes, formed by two layers of cuticle with an underlying hypodermis. A network of veins stretches along the wing - tubular thickenings of the chitinous coverings of the wing, giving it strength. The trachea enter the wing along the veins and
nerves. The pattern of wing venation is one of the important systematic characteristics of insects. Beetles have front wings - elytra - very thick and hard, they are called eli-tramp. They serve both for flight and to protect the thin membranous wings.
Rice. 148. Types of insect legs:
/ begagelpaia (ground beetles); // jumping bodies (enerchka); /// hiata-telny (mantis); /G burrowing (copper);
/ basin;
2
nerglug; 3 -
hip; / shin; 5
paw
Rice. 149. Structure of an insect wing:
/ zhnlkonanis wing; // - wing section;
/ ......copalilla vein;
2-
eubkoognl-
share; ,4
radial; / - medial;
5
....... cubitalpaia;
V - anal; 7
jugalpae;
N trachea
The flight of insects is varied: it can be flapping, soaring, fluttering, etc. The movement of the wings can be very frequent. Thus, a flying bee makes up to 440 strokes per second.
The abdomen of insects consists of (12 segments). In adults
The integument of insects, like other arthropods, is formed by a single-layer epithelium - the hypodermis and the chitinous cuticle secreted by it.
Nervous system consists of a complex suprapharyngeal paired ganglion, connected by means of a peripharyngeal nerve ring with a smaller subpharyngeal ganglion, from which a chain of paired nerve ganglia stretches along the body along its ventral side (a pair on each segment), connected by longitudinal nerve cords (Fig. 150) . A fusion of the nerve ganglia of adjacent segments is often observed. Nerves extend from the ganglia to various organs.
Sense organs Most insects have a complex structure. There are complex and simple eyes on the head. Compound eyes consist of many, sometimes up to 20 or more thousand, individual ocelli (ommatidis) and can perceive the shape and color of objects. The olfactory organs are located on the antennae, which often also serve as organs of touch. Not all insects have hearing organs.
Rice. 150. Nervous system of a bee:
/ - suprapharyngeal ganglion; 2 - ganglion I of the chest; ," i- united ganglion II, thoracic and I. II abdominal segments; 4 liy of the III abdominal segment
Rice. 151. Internal structure of an insect (cockroach):
/ - view from above; // - side view; / - pharynx; 2
- esophagus; 3 --
goiter; 4
- muscular stomach; 5
- blind processes of the intestine; 6
- midgut; 7 - hindgut; 8
- Malpighian tubules; 9
- dorsal vessel with a row of hearts; 10 -~
suprapharyngeal ganglion; //-ventral nerve cord; 12 -
testis; 13, 14
- accessory glands of the genital apparatus; 15
- trachea; 16
- salivary gland; 17
- its reservoir; 18
- spiracles; 19
- sympathetic nervous system
Digestive system. The alimentary canal is divided into anterior, middle and posterior sections. The anterior section includes the oral cavity, into which the salivary glands, pharynx and esophagus open. The posterior section of the esophagus often expands into a goiter, which serves to store food (Fig. 151). In many insects, the foregut ends in a muscular stomach, in which food is ground. Digestion and absorption of food occur in the midgut. Often several blind outgrowths of the intestine flow into it, serving to increase its absorption surface.
Organs of excretion insects are Malpighian vessels - thin, non-branching tubes that open into the intestine.
Respiratory system. Respiration in the vast majority of insects is carried out using tracheas. Air enters them through holes on the sides of the body - spiracles. The inside of the trachea is lined with a thin chitinous film with a spiral thickening (only the smallest tracheas lack it), which gives the trachea elasticity and prevents their flattening. The tracheae are connected by a number of longitudinal trunks. The entry and removal of air from them occurs by changing the volume of the abdomen by muscle contraction. The larvae of some insects (dragonflies, mayflies, etc.) living in water breathe through tracheal gills - thin-walled (often branched) abdominal outgrowths in which a network of tracheae is located. Sometimes larvae living in water have gills that lack tracheae; gas exchange occurs through their thin covers.
The circulatory system of insects is not closed. A long tube stretches along the back in the abdominal cavity, consisting of a number of pulsating chambers - hearts. In the thoracic region, the heart continues with a large vessel - the aorta. Blood enters the heart from the body cavity through paired lateral openings with valves. From the heart, blood moves through the aorta and through its final opening pours into the body cavity, washing all organs.
Reproductive organs. Insects are dioecious. In males, paired testes are located in the abdomen, from which vas deferens extend, connecting into an unpaired ejaculatory canal. The ovaries of females look like a bunch of tubes, gradually expanding downwards. They open into paired oviducts, which are connected below into a single vagina that opens outward. During mating, the male’s seed is introduced into the copulatory bursa of the female, then in some insects it enters the vagina through a special canal, where fertilization of the eggs occurs; in others, sperm from the copulatory bursa enters the spermatic receptacle, where it can be stored for a long time. From here, the seed enters the vagina in separate portions and fertilizes the eggs.
In these forms, the female can lay fertilized eggs for a long time after mating. Thus, the queen bee, after mating with a drone, produces thousands of fertilized eggs during her life (4-5 years) without re-fertilization.
The development of insects proceeds either without transformations or with incomplete or complete metamorphosis. During direct development (without transformations), which is typical for lower insects, eggs emerge from individuals that differ from adults primarily in their small size and underdeveloped genitals. In insects with incomplete metamorphosis (Fig. 152), eggs hatch into larvae with the features of an imago, but differing from them in smaller size, usually rudimentary wings and still poorly developed genitals. These larvae undergo several molts and eventually develop into adult insects without going through the pupal stage.
In insects with complete metamorphosis (Fig. 153), worm-like larvae emerge from the eggs, completely different from the imago. Having reached a certain age and size after a series of moults, they stop moving and feeding and soon turn into a pupa. The pupa is usually motionless or can make the simplest movements. Inside her body, a profound restructuring of the body occurs with the formation of tissues and organs of an adult insect. When this complex process ends, the integument of the pupa bursts and the imago emerges.
Many insects exhibit pronounced sexual dimorphism. Thus, small male moths have well-developed wings and a thin abdomen. The females of this butterfly are larger, their wings are reduced, and their abdomen is swollen.
In insects living in colonies, polymorphism often occurs, in which individuals of the same species have different structures depending on the role they play in the life of the colony. Thus, in the colonies of many termites, the ancestor of the family, the queen, is distinguished by a huge abdomen, which does not allow her to move, and she is fed by worker termites (Fig. 154). The queen lays several thousand eggs every day.
Rice. 153. Development of insects with complete reproduction (mulberry silkworm):
/ - butterfly; 2 caterpillar; 3 ..........cocoon; 4 ...... pupa cured without cocoon
Rice. 154. Polymorphism in termites:
/- worker; //--soldier; ///- winged male;
IV■-
a young female who has shed her wings after fertilization; V-~
adult female
Male termites do not live long. They fertilize the uterus. The bulk of the members of the colony are worker termites, distinguished by their small size and small heads: they build a termite mound, obtain food, and feed the larvae. Termite mounds are also home to soldier termites, which are easily recognized by their huge heads with powerful jaws; they fearlessly defend the colony from enemy attacks.
Ecology of insects. The vast majority of insects are land dwellers. On land, insects inhabit a wide variety of habitats. Many of them are true subterranean animals that feed on underground plant parts, decaying matter, or soil animals. A large number of insect species live in fallen leaves (forest litter). They are also numerous in the grass cover, where they find shelter and an abundance of food. Many insects stay on trees and bushes, eating leaves, shoots, seeds and fruits, sucking juices or gnawing into the wood of trunks. Finally, some insects spend a lot of time in flight, often rising with air currents hundreds or even thousands of meters above the surface of the earth. Aquatic insects live mainly in standing reservoirs and slow-flowing rivers. There are almost none of them in the seas.
Based on the time of greatest activity, insects are divided into daytime, twilight and nocturnal.
It has been noted that the insect fauna of tropical countries is much richer in species than the insect fauna of temperate and especially cold zones. This is explained primarily by the fact that insects are among the animals with variable body temperature. Therefore, in zones of temperate and cold climates, almost all insects fall into a long winter hibernation, to which only relatively few species have been able to adapt. But even in the warm season, climatic and weather conditions have a huge impact on various life processes of insects. For example, a corn borer caterpillar consumes 266 mm3/h at 20 °C, 95 at 12 °C, and only 22 mm3/h of oxygen per 1 g of mass at 0 °C. The gamma moth butterfly in the north of the European part of our country gives only one generation per year, in the middle zone - two, and in the south - three generations.
Weather conditions are among the main reasons for fluctuations in insect numbers from year to year. This is important to take into account when organizing the fight against insect pests of agriculture. They must be dealt with using various methods. Fluctuations in the number of insects are often also determined by the abundance or lack of food and animal migrations.
Depending on the number of insects, its distribution area can be divided into several zones:
zone of constant abundance of a given species (and for pests - also of constant and active harmful activity);
a zone of permanent habitat, but only periodically abundant in years with favorable living and breeding conditions. Malicious activities are expressed to varying degrees over the years;
an area where the insect is rarely found and does not harm crop production, but where in some years outbreaks of numbers and harmful activities are observed;
a zone where a given insect is not usually found, but occasionally appears, migrating from other zones during years of mass reproduction.
According to their lifestyle, insects can be divided into the following groups:
non-boring, feeding on plants, animals, rotting substances, corpses, manure, etc.;
According to the nature of their feeding, insects are divided into:
phytophages - herbivorous forms, which, in turn, are divided into those that feed on plant juices, leaves and shoots, fruits, seeds, roots, roots, etc.;
zoophages - insects that feed on animals;
coprophages - insects that eat animal dung and excrement;
pecrophages - insects that feed on corpses;
saprophages - insects that feed on rotting plant matter;
pantophagi are omnivorous insects.
Insects are distinguished by complex nervous activity. In their behavior, instincts are of particular importance - a set of sometimes very perfect unconditioned reflexes, i.e., such reactions of the body to irritations of the external environment that are not acquired by the experience of a given individual, but have developed historically over a long time and have become hereditary, innate. Sometimes instincts are very complex and determine the very appropriate behavior of an insect. For example, the ammophila sand wasp feeds its larvae with butterfly caterpillars. Having found the caterpillar, it thrusts its sting into those parts of the body where the nerve nodes of the abdominal chain are located. Damage to the nerve nodes does not kill the caterpillar, but paralyzes its movements. Then the wasp drags the motionless caterpillar into a pre-dug hole and lays its egg on it. The emerging larva feeds on the living, paralyzed caterpillar for a long time.
Rice. 155. Beneficial insects:
/ - hoverfly and its predatory larva; // -- lacewing and predatory larva; ///, IV- beetle beetle and its larva; V- ladybugs and their larvae; VI-
ground beetle; VII- rove beetle
Instincts reach particular complexity in social insects - ants, bees, termites, etc. In their colonies (representing the offspring of one queen), differentiation of individuals into several forms is usually observed: queens, drones, workers, soldiers, etc. Each of these groups performs in the colony has its own role and has its own responsibilities. In the colonies of some social insects, surprisingly complex and peculiar relationships are sometimes created between their members. For example, large Amazon ants attack colonies of other ants and capture their pupae. The ants hatched from them turn into “slaves” of the Amazons, ensuring the construction of the anthill, obtaining food, caring for the young Amazons and other work. Some tropical species of ants and termites create “mushroom gardens” in their nests, growing mushroom mycelium on a mass of finely chewed leaves and wood. Many ants cultivate root aphids, bringing them to their nest and planting them on the roots of plants, they “milk” them, forcing them to secrete special sugary substances by tickling their antennae.
But among insects there are many species that bring great benefits to humans. First of all, we must remember that pollination of many cultivated plants is carried out by bees, bumblebees, flower flies and other insects. Among insects there are many predators that destroy a lot of various pests of agricultural plants (Fig. 155). Ichneumonidae, egg eaters and some other hymenoptera insects lay eggs in the body or testicles of harmful insects, which leads to their death. Bees are bred by humans to produce honey and wax, and to pollinate crops. Silkworm caterpillars produce silk fiber, which serves as raw material for the production of natural silk. Many insects feed on the carcasses of animals, their excrement, various waste and rotting substances, clearing fields and forests. In tropical countries, some insects (locusts) are eaten.
Insects- a class of invertebrate arthropods.
External building.
Body insect consists of three parts: head, chest and abdomen. The integument is represented by the chitinous cuticle, hypodermis and basement membrane. The color of the integument of insects is determined by pigments contained in the cuticle or hypodermis.
On head from five fused segments of two antennae, eyes and mouth organs. Structure eye complex - faceted. Some insect species also have 1 to 3 simple eyes, which are located between the compound eyes. Mustache(antennae) are the organs of smell. Oral apparatus: upper lip (labrum), upper jaws (mandibles), lower jaws (maxilla), lower lip (labium). The oral apparatus includes the tongue (hypopharynx). The oral apparatus can be: gnawing, piercing-sucking, sucking and licking. The primary type is gnawing.
Breast comprises three segments: prothorax, mesothorax and metathorax. They leave her three pairs of legs, two pairs of wings. Limbs can be: grasping, digging, swimming, jumping and collecting. The limbs are articulated. The main segment of the leg is called the coxa, followed by the trochanter, femur, tibia and tarsus. Wings (2 pairs) are located on the back of the chest. Under the hard elytra there are membranous wings. The wings are protrusions of the body walls. The wing consists of two folds of skin covered with a cuticle and a cavity between them.
Abdomen consists of several segments, on its sides there are spiracles. The number of abdominal segments varies from 11 to 4. Lower insects have paired limbs on the abdomen; in higher insects they are modified into an ovipositor.
Internal structure.
Digestive system consists of the intestinal tract. The system itself begins from the oral apparatus and salivary glands. Next comes the foregut, which consists of the pharynx, esophagus and chewing stomach. Digestion and absorption of nutrients occurs in the midgut. Here food breaks down into simple organic compounds. The hindgut is divided into the small intestine (where glucose is broken down) and the rectum (where water is absorbed and excrement is formed).
Circulatory system In insects the circulatory system is not closed. The heart looks like a long tube; blood is sucked into it from the body cavity through the pores. Then it enters the aorta and flows into the body cavity, bringing nutrients.
Respiratory system. Through the spiracles, air enters the trachea. Tracheas are thin tubes that branch throughout all the organs of the insect. Gas exchange occurs through the walls of the trachea located in the tissues.
Nervous system consists of nerve ganglia, which are divided into: suprapharyngeal, subpharyngeal and abdominal nerve chains. The supraglottic ganglion is a brain that is divided into three parts - the forebrain (responsible for the eyes), the midbrain (responsible for the antennae) and the hindbrain (upper lip).
Excretory system. The main excretory organs are the Malpighian vessels (2 tubes) in the body cavity, one end ends in the body cavity and the final waste products from the blood are absorbed into them; hindgut. There is also a fatty body that extracts harmful substances from the blood, but does not remove them from the body.
Sense organs. Compound eyes, organs of touch (antennae), organs of smell, organs of taste. Many insects are able to make sounds and hear them. The hearing organs and organs that produce sounds can be located in any part of the body.
Reproduction and development.
Reproduction sexually. Internal sexual fertilization occurs. Parthenogenesis (aphids) is known for a number of species.
Insects - dioecious animals. Many insect species exhibit sexual dimorphism. Males produce sperm in their testes; females have ovaries with a large number of eggs.
Development insects: egg – larva – pupa – insect. Development is divided into two periods - embryonic, including the development of the embryo in the egg, and postembryonic, which begins from the moment the larva emerges from the egg and ends with the death of the insect.
Lesson summary "Class Insects". Next topic:
Adult insects are among the most mobile and active invertebrates. Everyone uses their legs: some move slowly, and some move at great speed. Several units developed the ability to jump using their powerful hind legs, while others became excellent swimmers, both on the surface of the water and underwater.
However, there is a mode of locomotion that is unique among invertebrates: flight. Wings gave insects freedom and helped them become the most diverse and numerous group of animals on the planet.
Body structure and movement
Most adult insects have three pairs of legs. They are fixed on the underside of the thoracic segments, a pair per segment. Although some species have modifications, for the most part insect legs consist of five parts: coxa (coxa), trochanter, femur, tibia, and tarsus.
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Some predatory insects actively hunt, while others lie low and hide to get close to an unsuspecting victim. When the distance is right, the tenacious front legs shoot out with lightning speed.
These differences do not matter, but they are significant when performing more specialized functions. Grasshoppers, for example, with larger hind legs, accordingly have more muscles on the thigh. Avoiding danger, they can easily jump to a height that exceeds the length of their body many times over. The only exception among their relatives is the mole cricket (Gryllotalpa), whose front legs are much larger than the hind legs, as they are adapted to dig the ground.
Swimming
![](https://i0.wp.com/kipmu.ru/wp-content/uploads/2014/09/Notonecta-850x1024.jpg)
Many aquatic insects move slowly, but some are more active thanks to the paddle-shaped appendages formed from the hairy fringe on their legs. In aquatic beetles, this fringe is usually located on the hind legs, and in the water bug (Notonecta) - on the front legs.
Dragonfly larvae, unlike adults leading an aquatic lifestyle, generally have an extremely modern method of movement in water. When something threatens them, they turn on the “jet engine”, pushing water out of the tip of their abdomen.
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Specific leg modifications
![](https://i2.wp.com/kipmu.ru/wp-content/uploads/2014/09/Mantis_sp.jpg)
In many insects that use their limbs for other purposes, their legs have undergone specific modifications. For example, in predatory mantises (Mantis sp) the front legs have evolved to grasp prey. Not only can they be instantly thrown forward, but they are also equipped with spikes along the inner edge, providing a death grip. The legs of the water bug Ranatra sp have undergone similar changes. The honey bee (Apis melifera) and many of its relatives have special devices on their hind legs for transporting pollen from flowers to the hive. Leg modifications are not always related to nutrition. For example, male swimming beetles (Dytiscus sp) have developed suction cups on their front legs, allowing them to hold a slippery female during mating.
Insect wings
Insect wings are a unique phenomenon in the world of invertebrate animals, and the ability to fly played a huge role in their successful development of terrestrial habitats on the planet. Unlike birds and bats, whose wings developed from their legs, the wings of insects are completely independent structures in relation to their legs. They are compacted outgrowths of the upper layers of the second and third segments of the thoracic region. These wings are supported by muscles, one end of which is attached to the base of the wing inside the chest, and the other to the inner surface of the chest wall. The strength of insect wings is provided by a network of supporting veins.
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Most adult insects have two pairs of wings, although there are exceptions. In the group of true flies, reduced and modified hind wings serve not for flight, but for balance. On the other hand, if we take beetles, their hind wings control flight, and the front wings form a hard case that protects the hind wings at rest.
Flight destination
Winged insects, even those with the most limited ability to fly, certainly use their wings to avoid danger. Those who fly more skillfully use flight for a variety of purposes: from settling in new places and feeding to finding a partner for mating and choosing a place to lay eggs.
Insects are impressive both in their speed and, in some cases, in the duration of their flight. Some butterflies and moths undertake extended seasonal migrations of hundreds, if not thousands of miles. The agrimony (Vanessa cardui) is the most famous example in Europe in this regard. Every spring, subsequent generations head north from their permanent habitats in Southern Europe and North Africa. In America, the Danaus (Danaus plexippus) is equally famous. Danaids spend the winter in Mexico, but each spring subsequent generations migrate as far north as Canada. At the end of summer and autumn there is a reverse migration to wintering areas.